1. Field of the Invention
This invention relates to measuring equipment for performing precision inspection operations of a repetitive nature, most commonly performed on precision surface plates and, in particular, to a portable measuring instrument designed for use as a reference in performing a multiplicity of such inspections.
2. Description of the Prior Art.
Precision measuring devices of the prior art include the Cadillac Height Master gage, calibrated gage block sets, digital height gages, etc., which are expensive and, in some cases, require a considerable amount of set up time. Such devices may be used in shop areas of a manufacturing plant to perform a limited number of in-process inspections, but because of their high cost, they are most often confined to an inspection department, laboratory or tool room area. Thus, precision in-process inspections are not usually performed and final inspections are most often performed on a statistical basis because of the problems associated with moving the production parts to a laboratory or tool room area for inspection. For this reason, the measurement may only be determined on a statistical basis whether a product run or production batch meets the design tolerances established for the product. Further, such procedures do not provide the number of inspections that may be necessary. Moreover, such procedures do not point up during the course of production the area in which production tolerances are exceeded. The use of precision measurement reference and measurement for in-process inspection is quite useful because appropriate tests may be performed in the production area and cause a reduction in manufacturing costs as defects are discovered and correction effected early in the production process. Further, it may be possible to effect a correction before a process goes completely out of tolerance thus saving a production run.